Heretofore, boom-type forklifts have utilized a telescoping boom to which was attached a typical carriage with two forks. The fork attachment was operatively connected to the boom by means of hydraulic cylinders which could be slaved to the cylinders operating the boom. In this manner, the fork attachment could be maintained in a relatively horizontal position regardless of the pivotal up and down motion of the boom.
When the boom was extended in a substantially horizontal position, the forklift attachment would be substantially vertical in order to maintain the fork tines which are connected to the attachment at a 90.degree. angle in a substantially horizontal position. Thus, the forklift attachment presented a very high profile when the boom was in a substantially horizontal position. This substantially limited the forklift's ability to load and/or unload pallets or containers densely packed in truck trailers or trailer mounted vans.
In view of the restrictions inherent in prior art forklifts, a variety of unloading methods have been used, all of which have drawbacks and disadvantages.
In using an ordinary forklift to unload pallets from a truck mounted container in the field, it was proposed to provide a ramp so that the forklift could enter the container and unload the cargo. This method has the obvious drawback of requiring a portable ramp and requiring that the forklift itself make several trips into and out of the container.
A "slip sheet" method of unloading pallets was also proposed in which a plastic or metal sheet was placed on the floor of the container and the pallets were placed on this sheet. When unloading the container the "slip sheet" would be pulled from the container onto a flatbed truck. Once on the flatbed truck ordinary forklifts would approach the cargo from the side of the truck and commence unloading the pallet. Besides the obvious problem of having the slip sheet tear, there was also the problem posed when the flatbed truck was not perfectly level or aligned with the container. These conditions would result in the slip sheet moving off to the side of the flatbed truck causing the pallets to fall.
In unloading missile pods from the container, it was customary to attach chains to the missile pods and drag them to the edge of the container until at least half of the missile pod extended out beyond the edge of the container. A first forklift would then engage the front of the missile pod to prevent it from falling while a second forklift would move in from the side of the missile pod and engage it at its approximate center of gravity so that it could be lifted from the container and transported to its ultimate location. This unloading method presented the hazard of precariously balancing a missile pod on the edge of a container and also necessitated the use of three pieces of machinery; one to pull the pods from the container, one to support the emerging end of the pod and one to engage the center of the pod and remove it from the container.
It is an object of the present invention to provide a forklift attachment that is specifically adapted for "unloading" fragile cargo such as ammunition pallets or missile pods from truck trailers or trailer mounted vans or containers.
It is also an object of the present invention to provide a forklift attachment having horizontally adjustable tines on the fork assembly.
It is yet another object of the present invention to provide leveling means for the fork assembly that is independent of the operation of the cylinders controlling the position of the boom.